From 4c06f800558b31071771cafda11c2389b92f883d Mon Sep 17 00:00:00 2001
From: Paul Norman <penorman@mac.com>
Date: Thu, 21 Jul 2022 18:47:11 -0700
Subject: [PATCH] Improve country label placement by splitting

By splitting MPs into polygons, taking the largest,
and finding a point in 4326 we get better points for
placing labels. 4326 does distort the placement, but
it does so in a way that results in better results
for most countries.
---
 project.mml | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/project.mml b/project.mml
index ab3966e0ae..44579837ff 100644
--- a/project.mml
+++ b/project.mml
@@ -1178,13 +1178,20 @@ Layer:
     <<: *extents
     Datasource:
       <<: *osm2pgsql
+      # By splitting MPs into polygons, finding the largest in real area, and
+      # finding a label point in 4326 we get better labeling points. 4326 does
+      # distort the placement, but it does so in a way that results in better
+      # results for most countries.
       table: |-
         (SELECT
-            ST_PointOnSurface(way) AS way,
+            (SELECT ST_Transform(ST_PointOnSurface(geom),3857)
+              FROM ST_Dump(ST_Transform(way,4326))
+              ORDER BY ST_Area(geom::geography) DESC
+              LIMIT 1) AS way,
             way_area/NULLIF(POW(!scale_denominator!*0.001*0.28,2),0) AS way_pixels,
             name
           FROM planet_osm_polygon
-          WHERE ST_PointOnSurface(way) && !bbox!
+          WHERE way && !bbox!
             AND name IS NOT NULL
             AND boundary = 'administrative'
             AND admin_level = '2'